In spite of the fact that an increasing number of patients are suffering from chronic obstructive lung disease, methods of noninvasive detection are developed to a limited extent. This study will develop and test clinically techniques utilizing sound transfer function of the lung for the identification of alternations in lung structure. Methodology of sound transfer analysis employing a frequency-sweep of induced signals has been developed and extensively tested in animals and has been demonstrated to reveal a sensitive and consistent pattern of alteration in sound transfer function of the lung resulting from increase in lung liquids. The same method of introducing audible sound into the upper respiratory tract of normal humans and in patients with pulmonary emphysema, chronic bronchitis, asthma, pulmonary fibrosis, and acute pneumonia will be utilized to characterize those disorders. The interrelationship of the induced and detected sound will be used to determine the transfer function of the lung. Classification and categorization of patterns of sound transfer will be correlated with clinical parameters and pulmonary function studies. This study will provide a new, useful, noninvasive technique for the identification of pulmonary diseases. Distinctive advantages of this system include the possibility of on-line data processing with immediate results available from one test compared to the multiple procedures used in pulmonary function testing. The hazards of electrical coupling and radiation do not exist. In addition, this simple procedure requires only minimal patient cooperation. These features provide a desirable technique for screening large numbers of people for lung disease. Data base will include recording and analysis of natural respiratory sounds in a studied group of patients.